Engines, including diesel engines, gasoline engines, natural gas engines, and other engines known in the art, may exhaust a complex mixture of air pollutants. The air pollutants may be composed of gaseous material (e.g., CO, NOx, etc.) and solid material, such as particulate matter. Particulate matter may include ash and unburned carbon particles and may sometimes be referred to as soot.
Due to increased environmental concerns, exhaust emission standards have become more stringent. The amount of particulate matter and gaseous pollutants emitted from an engine may be regulated according to the type, size, and/or class of engine. In order to meet these emissions standards, engine manufacturers have pursued improvements in several different engine technologies, such as fuel injection, engine management, and air induction. In addition, engine manufacturers have developed devices and systems for treatment of engine exhaust after it leaves the engine.
Such systems are often referred to as “after-treatment” systems. After-treatment systems may include after-treatment components, such as catalytic converters. For example, systems have been developed that employ Selective Catalytic Reduction (SCR) after-treatment solutions to minimize the amount of harmful constituents exhausted to the environment. Currently, the catalysts employed to convert nitrogen oxides (NOx) into diatomic nitrogen (N2) and water (H2O) in an SCR include, or are coated onto, either a ceramic or metallic substrate. Ceramics and metals each have advantages for use as catalyst substrates. Ceramic substrates, while typically more efficient, may provide inferior structural support. On the other hand, metallic substrates may provide superior structural support but may lack the surface properties (e.g., porosity) that provide the efficiency of a ceramic substrate.
Systems have been developed that provide ceramic substrates with improved strength by including a coating on the ceramic. For example, U.S. Patent Application Publ. No. 2005/0042151 (“the '151 publication”) discloses a ceramic catalytic substrate including a chemical/material coating on the inside. However, due to the brittle characteristics of ceramics, any failure of the ceramic substrate disclosed in the '151 publication could result in significant and even catastrophic damage. There remains a desire for a substrate for a catalyst or particulate filter that has strength without sacrificing efficiency.
Accordingly, the present disclosure is directed at improvements in existing catalyst and particulate filter substrates.